2-STEP PCR-BASED ASSAY FOR IDENTIFICATION OF BACTERIAL ETIOLOGY OF OTITIS-MEDIA WITH EFFUSION IN INFECTED LEBANESE CHILDREN

We developed and evaluated a two-step PCR-based assay with universal p rimers and genus- or species-specific primers for the detection of the most prevalent bacterial etiologies of otitis media with effusion (OM E) in children from Lebanese hospitals. These etiologies included Haem ophilus, Streptococcus, and Moraxella (Branhamella) catarrhalis, which were detected in middle-ear effusion (MEE) samples taken from childre n with OME. A total of 47 MEE samples were aspirated from 36 patients during insertion of a tympanostomy tube performed particularly for OME . The duration of effusion in all patients was greater than or equal t o 2 months. DNA was extracted from MEE samples, and PCR was initially done with DNA extracts by using the universal primers RW01 and DG74, w hich flank an similar to 370-bp fragment found in the 16S rRNA gene of all bacterial species. For the identification of specific bacteria, w e used in three separate reaction mixtures the following genus- or spe cies-specific primers: (i) a Haemophilus-specific probe (probe RDR125) as a primer along with DG74, (ii) a Streptococcus-specific primer (pr imer STR1; designed by us) along with DG74, and (iii) an M. catarrhali s-specific primer pair (primer pair MCA1-MCA2). Thirty-five MEE sample s (74.5%) gave the expected 370-bp band, indicating the presence of ba cterial DNA in the tested samples. Of the 35 PCR-positive samples test ed, 33 (94.3%) were positive for Haemophilus, 3 (8.6%) were positive f or Streptococcus, and 10 (28.6%) were positive for M. catarrhalis. Ten samples (28.6%) exhibited a mixed infection and were positive for bot h Haemophilus and M. catarrhalis. Culture was simultaneously performed for all 47 MEE samples. Ten of the 47 MEE samples (21.3%) exhibited b acterial growth. These 10 were PCR positive for bacterial DNA. The rem aining 25 PCR-positive samples were negative by culture, thus showing about 53% discordance between PCR results and those of culture. The PC R assay proved to be more sensitive than culture, more rapid, less cum bersome, and more cost-effective than the available PCR-Southern hybri dization-based assays.